The present invention relates to a method for regulating the density of pulp on the screen of a machine which forms a continuous web from a fibrous suspension, and apparatus for performing the method.
When forming a continuous web from a fibrous suspension on a screen, the pulp density influences the quantity of fibers deposited on the screen, both over the web width and also over the length thereof. It is known in the prior art to adapt the fiber deposition to various requirements by controlling the water drainage from the underside of the screen. However, this method becomes less and less effective as the apparatus speed increases and also as the surface weight decreases. Furthermore, another problem which occurs in forming the continuous web cannot be solved by this means; namely, the significant fiber deposits at the edges of the web and the prevention of fiber deposits beneath the edge of the screen. Other measures must be taken to combat these problems. The same is also true, for example, in avoiding the formation of knots and mats on the screen leather.